The present disclosure relates generally to an apparatus and methods for calibrating an imaging device and, in particular, to an apparatus and method for providing radiation within a near infrared light band of frequencies for calibration purposes.
Imaging devices are used in a variety of platforms (terrestrial, airborne, space, etc.) to take images of ground locations at hyper-spectral electromagnetic radiation frequencies, such as ultra-violet (UV) frequencies, visible (Vis) light frequencies, near infrared (NIR) frequencies, short wave infrared (SWIR) frequencies, medium wave infrared (MWIR) frequencies, and long wave infrared (LWIR) frequencies, etc. These imaging devices require scheduled or periodic calibration using hyperspectral calibrators. Traditional hyperspectral calibrators can be problematic for use in resource-constrained platforms such as space platforms because they can take up a significant portion of the volume and weight of the platform, and require continuous power in order to provide accurate and repeatable frequency and radiant power during the calibration process. Traditional bulbs used in integrating spheres for visible, NIR and SWIR calibration devices tend to suffer from mechanical fatigue and fracture after cycling on and off over thousands of cycles, thereby requiring the platform to carry multiple bulbs for reliable mission completion. For calibrations that utilize the solar reflection off of a diffuse reflector, additional equipment is required to monitor the degradation of the spectral properties of the reflector. Such equipment therefore requires additional volume and weight from an already resource-constrained platform.